Flow Stress Constitutive Model of Ultra Low Carbon Steel in Warm Deformation

Abstract

Warm rolling technique of ultra low carbon steels is a new technology for metal forming. In order to study the flow stress of ultra low carbon steels in warm deformation, experiments of warm deformation of this grade were carried out on a hot simulation machine with the deformation temperature of 750 to 950°C, and strain rate of 1 to 70 s−1. The experimental results have shown that the variation of flow stress with temperature in warm deformation is different from that in austenite deformation under high temperature, although the influences of strain rate and strain on flow stress in warm deformation of ULC steels are similar to those in austenite high temperature forming. A new flow stress constitutive model suitable to ferrite deformation of ultra low carbon steel is deduced in the paper on the basis of theoretical analysis and an actual flow stress model for ULC steels is obtained on the basis of experimental results. The comparisons between prediction values of new model and test values have proven that the new flow stress constitutive models given in the paper have higher precision when they are used to describe the flow stress variations of ULC in warm deformation.